The textbox value of the RadDatePicker control always
conforms to the date format. So the only way to stop the autocorrection in your case is to set a different date format.
the Telerik team
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Public Issue Tracking
system and vote to affect the priority of the items.